You are absolutely right. I have shown here the example of a type parameter without type-bound procedure.
But a derived type without type-bound procedures is only Fortran 90 and that is not what I want.
It seems that there is really no solution at the moment. Either I have to wait until the problems with gfortran are fixed (in fact the problems are not fixed since Fortran 2003 until today), or I have to do without gfortran.